and both location are connected through gre tunnel. now from location A can i be able to access whole network 192.168.14.0 of location B. plz assume that port 47 has been forwarded on both side of router.

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pawanopensourceAuthor Commented: 2010-01-05

one thing more the computers on which ill be configuring gre tunnel at both locations both computers r having one ethernet card.

It is not port 47 it is protocol type 47 there is a significant difference.

It all depends on what the location A and location B systems do. i.e. if these systems behave as routers and can not be behind a router, than the answer is yes that the GRE setup will allow access from a system with IP 192.168.14.x to reach a system with IP 192.168.15.x.
If however, each system is an individual workstation, that all the GRE tunnel will do is allow systemA to connect/access systemb and vice versa.

The linux firewal (iptables) would need to be configured to allow protocol type #47 packets to pass through and will be handled by the kernel/ipchains/gre_kernel module

I.e. the connection at each location would be IPS (intrusion Prevention system i.e. snort)

What type of routers do you have at each location?
You may want to setup a GRE PPTP connection then.
The problem is that you would then need to setup static routes on the router at each location to reroute The remote LAN directed traffic back to the linux box that will be establishing the GRE/PPTP connection.

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pawanopensourceAuthor Commented: 2010-01-06

at both end i am having simple adsl router. its not like cisco or juniper, its a simple adsl router.
ok what ill do is that on both pc on which ill configure gre tunnel ill attach two lan cards on both computer.

Location A

eth0 will be connected to adsl link
eth1 will be connected to switch so now gateway for lan of lacation A will be eth0 ip address

same with location B

now after doing this can i be able to access whole network of location A from location B and vice versa.

Before going to the GRE setup, make sure your linux system is setup and functions as a router. i.e. LAN users can access the net. Access to the LAN systems from the outside is not allowed. Your WAN interface is secured i.e. iptables are setup and running. Depending on your linux distribution, you may want to make sure that SELinux is enabled as well as have strong passwords if you have ssh open on the WAN eth0 side.